Within DRYvER we aim at generating a so far not existing impression on the chemical composition and diversity of particulate organic matter in six river networks. The tool of our choice is FTIR microscopy, allowing us to distinguish variously processed leaf litter particles, soil residuals and the occasional microplastic fiber. Tuning this microscopic method to efficiently achieve chemical fingerprinting for the many samples ahead of us in DRYvER is the lab challenge for the winter months.